Gas generator

ABSTRACT

A GAS GENERATOR, SUITABLE FOR FILLING INFLATABLE STRUCTURES IN THE PRESENCE OF HUMANS HAS A SPECIAL, NONTOXIC, SOLID FUEL IN AN ORIFICED PRESSURE VESSEL, IGNITION MEANS THEREFOR, AND COOLANT MEAN FOR COOLING THE GASES PRODUCED ON COMBUSTION OF THE FUEL BEFORE THEY ENTER AN INFLATABLE STRUCTURE.

Sept. 19, 1972 F. E. SCHNEITER ETA!- 3,692,495

GAS GENERATOR Filed June 19, 1970 4 Sheets-Sheet 1 INVENTORS: FEED E 5CH/VE/TEE Sept. 19, 1972 F. E. SCHNEITER ETAL 3,692,495

GAS GENERATOR 4 Sheets-Sheet 2 Filed June 19, 1970 Sept. 19, 1972 F. E. SCHNEITER ET 3,692,495

GAS GENERATOR 4 Sheets-Sheet 3 Filed June 19 1970 N 5 4 wfi u 3% M m vwaa T w Wm 16/... 5 505 6 52w 0 an HM 2 w 5 Sept. 19, 1972 F. E. SCHNEITER ETA!- 3,692,495

GAS GENERATOR Filed June 19, 1970 4 Sheets-Sheet 4' INVENTORS: FEED E SCH/VE/TEE HOW 6WD L JOAGEA/SE/V [EL/1ND E 0/7V/5 United States Patent Oflice Patented Sept. 19, 1972 3,692,495 GAS GENERATOR Fred E. Schneiter, Ogden, Howard E. Jorgensen, Hyrum, and Leland E. Davis, Brigham City, Utah, assignors to Thiokol Chemical Corporation, Bristol, Pa. Filed June 19, 1970, Ser. No. 47,788

Int. Cl. Billj 7/00 US. Cl. 23-281 3 Claims ABSTRACT OF THE DISCLOSURE A gas generator, suitable for filling inflatable structures in the presence of humans has a special, nontoxic, solid fuel in an orificed pressure vessel, ignition means therefor, and coolant means for cooling the gases produoed on combustion of the fuel 'before they enter an inflatable structure.

CROSS REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention relates to gas generators; and par ticularly to solid-fuel gas generators suitable for filling inflatable structures in the presence of humans.

The use of inflatable structures is becoming increasingly common. Although certain of these, such as various recreational equipment and inflatable furniture can be filled manually by an air pump, other inflatable equipment such as emergency life rafts must be quickly and automatically inflated. Conventional means of inflating such equipment has commonly included compressed gas in a pressure vessel, opened by mechanical or explosive means.

Of particular interest in the present invention is its use for inflating safety cushions for passenger-carrying vehicles. Such cushions are installed in a vehicle and are designed to be inflated rapidly and automatically to protect human occupants in event of a collision of the vehicle with some other object. Apparatus of this general nature are known in the prior art. For example, US. Pat. 3,336,045 to Y. Kobori describes a cushion device that is inflatable by a solid-fuel gas generator using an undesignated explosive" material for the fuel. US. Pat. 3,450,414, to the same inventor, shows a similar device wherein the source of gas cited is dichlorodifluoromethane (Freon l2), liquid propane, and solid ethyl alcohol. Many other patents show inflatable cushions wherein the source of gas is a container of compressed gas that is opened in response to collision by some explosive means.

The compressed-gas type of inflation device has a number of disadvantages; (1) It is relatively bulky and difficult to package neatly in places such as steering columns; (2) Automobile manufacturers regard highpressure containers of compressed gas, especially one equipped with explosive opening means, as a hazard on assembly lines; (3) They are also a hazard in shipping, storage, and handling; (4) They tend to be unreliable because of the ever-present possibility of leakage, especially after several years in an automobile; and (5) The pressure within the container can he dangerously increased by high ambient temperatures.

For these reasons, the solid-fuel gas generator is considered to be the superior source of gas for inflation of safety cushions: it can be contained in a much smaller package than compressed gas; it can remain reliable over long periods of time; and, if it is relatively insensitive to temperature and shock, it can be considerably safer than the compressed-gas type of inflation device.

However, the gases produced must also be nontoxic, because of the danger of rupture in the inflatable cushion; and it must produce gases that are cool enough to avoid burning the vehicle occupants. The source of gas must be capable of inflating the cushion within about 30 milliseconds after a collision signal is received. In a gas generator, this requirement for rapid inflation almost necessitates use of a fuel that is consumable at flame temperatures of the order of 2500 C. 0n the other hand, the violence of a typical collision forces the vehicle occupant deeply into the cushion and into intimate contact with the surface thereof. Hence, unless specific cooling means were provided to lower the temperature of the gases, the occupant would receive severe burns from the surface of the cushion. These two important problems, the toxicity and temperature of the inflating gases, have apparently received no consideration in the prior art.

SUMMARY OF THE INVENTION The present invention, which is primarily directed toward overcoming these disadvantages of the prior art devices, provides a solid-fuel gas generator that produces nontoxic gas and that has specific, effective cooling means for lowering the gas temperature to a point that is safe for the vehicle occupant. The cooling means include the use of heat sinks to absorb heat from the inflating gases, mixing the gases with cooling fluids, and passing them through materials that react endothermically to produce cooling gases that mix therewith.

The principal objects of the invention are to provide a source of gas to fill inflatable structures, that is reliable over long periods of time, nonhazardous during prolonged storage, nontoxic, and free from excessively high temperatures. Important features of the invention are its compact size and easy replaceability.

These and other objects and advantages of the invention will be noted as the following detailed description is read with reference to the accompanying drawings. Any unmodified part will be designated by the same number throughout the disclosure.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view showing how the invention is installed in a typical automobile;

FIG. 2 is a central section in side elevation of a first embodiment of the gas generator;

FIG. 3 is a full cross section taken on line 3-3 of FIG. 2;

FIG. 4 is a longitudinal section of a second embodiment of the gas generator;

FIG. 5 is a cross section taken on line 5-5 of FIG. 4;

FIG. 6 is an end view of the invention shown in FIG. 4;

FIG. 7 is a view, principally in longitudinal section, of a third embodiment of the gas generator;

FIG. 8 is a cross section taken on line 8-8 of FIG. 7;

'FIG. 9 is a second cross section taken on line 9-9 of FIG. 7;

FIG. 10 is a longitudinal section of a fourth embodiment of the gas generator; and

FIG. 11 a cross section taken on line 11-41 of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the invention is typically installed in a steering column or in some other convenient place wherein it will be positioned to cushion the force of a collision for an occupant of the vehicle. The gas generator 14 is shown in broken lines, and an inflatable cushion 15 is shown by a solid line in its normal condition. The broken line 15a indicates the fully inflated condition of the cushion 15. Devices for generating an electric signal in response to a collision are well known, and are not a part of the present invention. The most common instrument for this purpose is some kind of accelerometer that closes a switch in an electric circuit when unusual deceleration is experienced in the vehicle.

FIGS. 2 and 3 show a first embodiment of the novel gas generator 16. It includes a housing 17 made of a solid, cylindrical piece of aluminum, and having two parallel bores 18 and 19 therein. A solid fuel 20 is bonded into the larger bore 18 (which is a pressure vessel, defining the combustion chamber) in the form of strips or bars as shown in FIG. 2. Small ducts 21 connect the two bores so that gases may flow from one to the other. An ignition composition 22 fills the smaller bore 19 which comprises the ignitor enclosure; and a small electric squib 23 in intimate contact with the ignition composition 22 has electrical conductors 24 extending through the base 25 of the housing 17. A discharge orifice 26 leads from the larger bore 18 to the exterior of the housing 17. A baflie 27 that acts both as a diffuser and heat sink to absorb heat from the inflating gas is positioned above the orifice 26 by brackets 28, that are welded to the 'baflle 27 and are fastened to the housing 17 by screws 29. Edges 30 of the cushion 15 may be welded to the sides of the housing 17. The balfle 27 may be made of any material having a high rate of thermal conductivity, such as brass, bronze, copper, or aluminum. The outer ends of the bores 18 and 19 are threaded and are sealed by threaded plugs 31 and 32. The housing 17 is externally threaded at its base for engagement in a threaded recess 33 in the steering column 34.

On receipt of an electric signal, the squib 23 ignites the initiating composition 22 which, in turn, generates flaming gases that pass through the ducts 21 to ignite the solid fuel 20. Gases from combustion of the fuel 20 then pass through the orifice 26 and impinge upon the bafile 27 which both difluses the gases and cools them by absorption of heat therefrom. This cooling action is enhanced by the heat-sink nature of the housing 17, also being preferably made of a solid block of aluminum. The diffusing action of the baflle 27 is primarily intended to avoid damage to the cushion 15; but, by expanding the gases, it naturally cools them further. The summation of these cooling actions of the gases can lower the temperature thereof from about 2,372 F. to about 230 F.

The squib 23 is made of a small-diameter, resistance wire 35 surrounded by a small amount of an initiating composition 36 made of: 50 percent by weight of lead styphnate, 24 percent of potassium perchlorate, 24 percent of powdered zirconium, and 2 percent of an organic binder, such as VYLF, manufactured by Union Carbide.

A typical ignition composition 22 comprises, by weight:

Percent Boron powder 23.86

Potassium nitrate 71.17 Granular nylon (such as Du Pont Elvarnide Powdered graphite 0.99

The granular size of this material is controlled to range from 42 to 80 standard mesh.

The solid fuel 20 may be any one of a family of combustibles similar to solid propellants for rockets, having a binder that is a highly-oxygenated polymer containing only carbon, hydrogen, and oxygen; a curing agent containing the same elements; and either potassium chlorate or potassium perchlorate as the oxidizer. The binder to oxidizer ratio is adjusted to produce upon combustion a gas having less than 1.1% carbon monoxide, less than 1.0% methane, and only traces of hydrogen. No other toxic or flammable materials are present in the inflation gases. These compositions are described in greater detail and claimed in the copending application for patent titled Solid Fuel for Gas Generators" by R. Reed et al., cited previously herein. A typical composition of this solid fuel is, in percentage by weight.

Percent Formrez F-l (C Ha O saturated, carboxyl-terminated, polyester liquid poly- This formulation is the result of extensive laboratory r mixing and testing for desired combusion products, processing properties and mechanical properties. The liquid ingredients are placed in a mixer, and the finely-divided potassium perchlorate is gradually added as they are being agitated. After the mixing has been completed, the fuel is pressed into forms and cured at 135 F. for 72 hours. Upon completion of the cure, the fuel is removed from the forms and cut into strips for use in the gas generator.

Measured combustion products typical for this fuel when burned in 4,000 p.s.i. pressure vessel are, in percentage by Weight:

Oxides of nitrogen-less than p.p.m.

When the vehicle is subjected to collision, the cushion 15 will be inflated within about 30 milliseconds after impact. Experiments have indicated that this is sufficient time for the cushion 15 to perform its function of protecting the vehicle occupant from collision with the inside of the vehicle. Since the inflated cushion 15 would be a handicap to the occupant after it has served this purpose, provision is made for deflating it immediately. The primary mechanism for accomplishing this is porosity of the material from which the cushion is made. Alternatively, valve means, not shown, may be incorporated into the cushion 15. The deflating eflect of the escaping gas is enhanced by the fact that the gas will be cooling at the same time and, therefore, decreasing in volume.

The embodiment of the gas generator shown in FIGS. 4, 5, and 6 differs from that already described primarily in that cooling of the generated gases is not accomplished by heat absorption, but by mixing a cooling substance with the gases before they are expelled into the cushion 15. A tubular housing 37, closed at both ends, has a transverse partition 38 that forms an enclosure defining a small mixing chamber 39. The space between the aft end 40 of the housing 37 and the partition 38 is further divided by a longitudinal partition 41, that is filled with holes 42. A coolant chamber 43 is defined by the coolant container formed by the partition 41 and the housing 37, and is occupied by a flexible bladder 44 filled with a coolant 45, such as water. The forward end of the bladder 44 is fixed into the transverse partition 38, where it terminates in a nozzle 46 that is sealed by an easily-removable plug 47 in the orifice 48 and is canted toward the center of the mixing chamber 39. The other chamber 49 formed by the longitudinal partition 41 is the combustion chamber and contains the solid fuel 20 in the form of long strips in parallel arrangement, each bonded at one edge to the partition 41. A long tube 50 containing the ignition composition 22 and the electric squib 23 is closed at both ends and fixed to the wall of the combustion chamber 49 opposite the solid fuel 20. This tube 50 has two parallel rows of small orifices 51 arranged to direct burning gases from the ignition tube onto the solid fuel 20 for ignition thereof. The electric conductors 24 of the squib 23 pass through the aft end 40 of the housing 37, as shown in FIG. 4. The squib 23 and the ignition composition 22 are identical with those of FIGS. 1, 2, and 3, as is the solid fuel 20. A first discharge orifice S2 in the portion of the transverse partition 38, that helps to define the combustion chamber 49 is also canted toward the center of the mixing chamber 39 in opposition to the coolant orifice 48. An internal baffle plate 53 is fixed on the inside of the forward end 54 of the housing 37 by a short tube 55 filled with holes 56. The main discharge orifice 57, whereby gases emerge from the gas generator to fill the inflatable cushion is located in the center of the forward end 54 of the housing 37 in alignment with the internal bafile 53. An external baffle 27 is also positioned in alignment with the orifice 57 and fixed to the forward end 54 of the housing 37 by brackets 58.

Upon receipt of an electric signal, the squib 23 fires and ignites the ignition composition 22, which, in turn, produces flaming gases that pass through the orifice 51 to ignite the solid fuel 20. This fuel produces large quantities of gas, which simultaneously passes through the holes 42 in the longitudinal partition 41 to pressurize the bladder and through the canted orifice 52 into the mixing chamber 39. This pressurization of the bladder 44 expels the plug 47 in the bladder nozzle 46 and causes coolant to impinge on the stream of gases emerging from the combustion chamber 49. Further mixing of the combustion-chamber gases with the coolant is promoted by the internal bafile 53, which creates considerable turbulence in the mixture before it passes through the main discharge orifice 57. The emerging gases are further cooled and diffused by their impingement on the external bafile 27, as described for the embodiment of FIGS. 1, 2, and 3. The wall of the cushion 15 may surround the forward end of the tubular housing 37 in sealed relationship therewith, as shown in FIG. 4, so that the gases emerging from the housing 37 will pass into the cushion is. The coolant 45 may also be any aqueous solution of a nontoxic salt, such as calcium chloride, or sodium carbonate. A third embodiment of the gas generator 14 is shown in FIGS. 7, 8, and 9. In this embodiment, the gases generated by the solid fuel pass through solid particles that react endothermically to produce cooling gases that mix with those produced by the solid fuel. A tubular baflle 59, closed at both ends, has a multiplicity of holes 60 in one side thereof. A smaller tube 61 serves as a housing for the gas generator proper. This tube 61 fits into the larger, bafile tube 59 so that its ends are closed by the end members 62 thereof, and the gas-generator-housing tube 61 is fixed at one side to the inside of the baflle tube 59 opposite the holes 60 therein. The housing tube 61 is divided into two chambers by a transverse partition 63. One of these chambers is a combustion chamber 64. The igniter 65 comprises a small tube 66 filled with the ignition composition 22 in the presence of an electric squib 23, which has electric conductors 24 that are externally accessible. The igniter tube 66 is fixed to the inside of the wall of the combustion chamber 64. Opposite the igniter 65, strips of solid fuel are radially positioned along the wall of the combustion chamber 64 and are bonded thereto. When the squib 23 is fired, flaming gases from combustion of the igniter composition 22 pass through two rows of holes 67, that are directed toward the solid fuel 20 for ignition thereof. Gases from combustion of the solid fuel 20 then pass through an orifice 68 in the partition 63 into a diffuser tube 69. The diffuser 69 is relatively small in diameter, is centrally positioned in the coolant chamber 70, extends longitudinally thereof, and is filled with a multiplicity of holes 71 which allow gases from combustion of the solid fuel 20 to difi'use through particles of solid coolant 72 that fill the space in the coolant chamber 70 around the diffuser tube 69. A multiplicity of holes 73 in that portion of the gasgenerator housing 61 which forms the wall of the coolant chamber 70 permit the cooled gases to pass into the battle tube 59, where they are further diffused and cooled, and into the inflatable cushion 15. A mounting stud 74 assists in installing the invention in a vehicle.

The particles of solid coolant 72 are made of dry chemicals that react endothermically to liberate gas in the presence of heat. Specific materials which are suitable for this purpose include sodium bicarbonate (NaHCO ferrous oxalate (FeC O -2H O), and oxalic acid These materials have fairly low decomposition temperature, are highly endothermic, and liberate gases without significant toxicity. The form of the coolant particles is critical to the function of achieving adequate cooling in the short period of time required for inflation of the cushion 15.

A fourth embodiment of the invention is shown in FIGS. 10 and 11. A tubular housing 75 is closed at the discharge end 76 by an end plate 77 having a main discharge orifice 78 therein, and it is closed at the other end by threaded engagement with an igniter plug 79. The igniter 80 is built into a bore 81 in the plug 79 which terminates in an orifice 82. This orifice can direct flaming gases from the igniter 80 onto the solid fuel 20 that is positioned in the combustion chamber 83 in the manner that has been described for the previous embodiment of the invention. The combustion chamber 83 is formed adjacent the igniter plug 79 by a transverse partition 84 having an outwardly-canted first-discharge orifice 85 therein. The orifice 85 is sealed by adhesive tape 86. The igniter 80 contains the same elements that have been described for previous embodiments of the invention, i.e., the electric squib 23 and the igniter composition 22. The igniter orifice 82 is sealed with tape 86, which is easily blown off by the hot gases when the igniter is fired.

A bafile 27, identical to that shown in FIG. 4 is mounted externally over the discharge orifice 78 and spaced therefrom by brackets 58, each fixed at one end to the bafile 27 and at the other end to the end plate 77. It serves the same purpose as the baffie shown in FIG. 5. A short tube 88 is mounted internally on the end plate 77 in alignment with the main discharge orifice 78. The inner end of this tube 88 is sealed with an easily removable seal, such as adhesive tape 89. A coolant chamber 90, formed between the end plate 77 and the partition 84 is filled with a coolant material 91. The coolant material 91 may be in liquid form, such as an aqueous solution of calcium chloride. Alternatively, solid coolant materials, such as those described for the embodiment shown in FIGS. 7, 8, and 9 may be used. If solid particles are used, some means of retaining them in the gas generator is desirable, such as a screen (not shown) that may cover the end of the tube 88 in addition to, or in place of, the tape 89.

In operation, an electric signal responsive to collision will fire the squib 23 to ignite the ignition composition 22, which in turn will ignite the solid fuel 20. Hot gases from combustion of the fuel 20 are directed, in swirling motion, through the coolant material by the orifice 85 in the partition 84. As pressure is built up in the coolant chamber 90, the tape 89 on the tube 88 is quickly removed to allow escape of the gases into the inflatable cushion 15 via the diffusing baifle 27. Tape seals 87 and 86 on the igniter orifice 82 and partition 84, respectively, are also very quickly removed by the hot gases from the igniter 80 and the solid fuel 20. Reaction of the hot gases with the coolant materials described is highly endothermic and, although this cooling action would tend to diminish the volume of the gases generated by the solid fuel 20, this volume may be even increased by particles and vapors added by the coolant materials. These coolant materials are' more thoroughly described, and are claimed, in a copending application for patent titled Coolants for Gas Generators by Graham C. Shaw and Russell Reed, Jr.

An invention has been described that constitutes an advance in the art of gas generators for filling inflatable structures in the presence of humans. Although the foregoing description has been specific with regard to details, it should be noted that many such details may be re placed by equivalent means without departing from the scope of the invention, as it is defined in the appended claims.

The invention claimed is:

1. A gas generator for filling inflatable structures in the presence of humans comprising:

a tubular housing having closed ends with a main discharge orifice in one end;

a transverse partition in the tubular housing defining a mixing chamber adjacent the main discharge orifice;

a longitudinal partition in the housing extending from the transverse partition to the closed end opposite the main exhaust orifice, the longitudinal partition defining a combustion chamber on one side, and a coolant chamber on the other side thereof with an opening therein to allow pressure from the com bustion chamber to enter the coolant chamber, a first discharge orifice being in the transverse partition between the combustion chamber and the mixing chamber and being canted toward the center of the mixing chamber;

a solid fuel in the combustion chamber;

ignition means in the combustion chamber for igniting the solid fuel;

a flexible bladder filled with liquid coolant in the coolant chamber;

a sealed nozzle on the bladder extending through the transverse partition and canted toward the center of the mixing chamber, so that, when the bladder is pressurized by combustion gases from the solid fuel, a stream of coolant therefrom may impinge on the stream of gas emerging from the first discharge orifice;

an internal bafile fixed in the tubular housing and spaced over the main exhaust orifice to promote thorough mixing of gas and coolant in the mixing chamber; and

an external bafile fixed to the tubular housing and spaced over the main exhaust orifice for further cooling and diffusing of gas emerging therethrough.

2. A gas generator for filling inflatable structures in the presence of humans comprising:

a tubular housing closed at both ends;

a transverse partition, having a discharge orifice therein, that divides the housing into a combustion chamber and a coolant chamber;

a solid fuel in the combustion chamber;

ignition means in the combustion chamber for igniting the solid fuel;

particles of solid coolant in the coolant chamber, that are capable of reacting endothermically with gas emerging from the discharge orifice when the solid fuel is burned;

a diffuser tube filled with holes and extending from the discharge orifice into the coolant chamber to promote rapid contact of the gas with the coolant particles, that are distributed between the dilfuser tube and the housing wall, the housing also being filled with holes in that portion thereof which bounds the coolant chamber, whereby the cooled gases may emerge; and

a tubular baflle, closed at both ends, having holes therein, and enclosing at least the portion of the housing that forms the coolant chamber, whereby gases emerging from the coolant chamber may be bafiied before entering a device to be inflated.

3. A gas generator for filling inflatable structures in the presence of humans comprising:

a tubular housing, closed at both ends, except for a main discharge orifice in one end;

a transverse partition in the housing dividing it into a combustion chamber and a coolant chamber adjacent the main discharge orifice, an outwardly-canted orifice being in the partition to direct gas from the combustion chamber against the wall of the coolant chamber to create a swirling motion to cause the gases to lose energy;

a solid fuel in the combustion chamber;

ignition means in communication with the combustion chamber for igniting the solid fuel;

a short tube fixed to the inside of the housing and surrounding the main discharge orifice, the tube extending into the coolant chamber so that it cooperates with the canted orifice in the partition by forming an annular space that tends to delay emergence of the gases from the coolant chamber and promotes the swirling motion thereof as initiated by the canted orifice;

rupturable sealing means over one end of the short tube, to be broken when gases are produced;

rupturable sealing means over the orifice in the partition to be broken when gases are produced; and

a battle mounted externally on the tubular housing, spaced from the main discharge orifice in alignment therewith, to promote further cooling and diffusion of gas discharged therefrom.

References Cited UNITED STATES PATENTS 3,305,319 2/ 1967 Kowalick et a1 23-281 3,515,518 6/1970 Halstead et al. 2328l 3,558,285 1/1971 Ciccone et al. 23-28l 3,066,014 11/1962 White et a]. 23281 3,336,045 8/1967 Kobori 280 AB 2,494,131 1/1950 Jackson et a1 23 281 2,779,281 1/ 1957 Maurice et a1 102--39 3,532,359 10/1970 Teague et a1 280150 2,816,419 12/1957 Mueller 23-281 X JAMES H. TAYMAN, I 11., Primary Examiner US. Cl. X.R. 

